SERVER-30379 Add health log.

1 files changed, 93 insertions, 0 deletions

diff --git a/src/mongo/db/catalog/health_log.h b/src/mongo/db/catalog/health_log.h
new file mode 100644
index 00000000000..84de0e215ab
--- /dev/null
+++ b/src/mongo/db/catalog/health_log.h
@@ -0,0 +1,93 @@
+/**
+ *    Copyright (C) 2017 MongoDB Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the GNU Affero General Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#include "mongo/base/disallow_copying.h"
+#include "mongo/db/concurrency/deferred_writer.h"
+#include "mongo/db/service_context.h"
+
+namespace mongo {
+
+class HealthLogEntry;
+
+/**
+ * The interface to the local healthlog.
+ *
+ * This class contains facilities for creating and asynchronously writing to the local healthlog
+ * collection.  There should only be one instance of this class, initialized on startup and cleaned
+ * up on shutdown.
+ */
+class HealthLog {
+    MONGO_DISALLOW_COPYING(HealthLog);
+
+public:
+    /**
+     * Required to use HealthLog as a ServiceContext decorator.
+     *
+     * Should not be used anywhere else.
+     */
+    HealthLog();
+
+    /**
+     * The maximum size of the in-memory buffer of health-log entries, in bytes.
+     */
+    static const int64_t kMaxBufferSize = 25'000'000;
+
+    /**
+     * Start the worker thread writing the buffer to the collection.
+     */
+    void startup(void);
+
+    /**
+     * Stop the worker thread.
+     */
+    void shutdown(void);
+
+    /**
+     * The name of the collection.
+     */
+    static const NamespaceString nss;
+
+    /**
+     * Get the current context's HealthLog.
+     */
+    static HealthLog& get(ServiceContext* ctx);
+    static HealthLog& get(OperationContext* ctx);
+
+    /**
+     * Asynchronously insert the given entry.
+     *
+     * Return `false` iff there is no more space in the buffer.
+     */
+    bool log(const HealthLogEntry& entry);
+
+private:
+    DeferredWriter _writer;
+};
+}